Catalyst composition and hydroprocessing of oils using same

ABSTRACT

A catalyst composition comprising an alumina-aluminum phosphate-silica support bearing a halogen, a Group VI metal and a Group VIII metal in which the support has an average pore radius of from about 10  ANGSTROM  to about 300  ANGSTROM , a surface area ranging from about 50 m2/g to about 400 m2/g and a pore volume of about 0.1 to about 1.5 cc/g. The catalyst composition is used for hydroprocessing oils and possesses significant hydrodenitrification activity.

FIELD OF THE INVENTION

This invention relates to a catalyst useful in the hydroprocessing ofoils and to the use of such catalyst in such processes. Moreparticularly, this invention relates to a catalyst compositioncomprising an alumina-aluminum phosphate-silica support and to theproduction of a denitrified lubricating oil of high viscosity indexusing such catalyst.

BACKGROUND INFORMATION

The production of a stable, white lubricating oil of high viscosityindex in good yield from a heavy lubricating oil distillate normallyrequires a two-stage process utilizing two different catalysts. Thefirst stage is employed to effect the primary charge stock alterations,i.e., saturation of aromatics, cracking naphthenes, and isomerization ofparaffins. A significant portion of the nitrogen and sulfur are alsoremoved in the first stage. The second stage, which follows aninterstage dewaxing of the first stage effluent, is a mild hydrogenationstep employing a catalyst which is sensitive to high concentrations ofhydrogen sulfide and ammonia. In this stage, additional amounts ofsulfur are removed and light stability is imparted by further reductionin the levels of nitrogen and aromatics.

To produce an acceptable first-stage product, the catalyst must havehigh hydrogenation and isomerization activities but without theextensive hydrocracking that would result in excessive loss of materialfrom the lubricating oil boiling range. It should also have goodactivity for nitrogen and sulfur removal and at the same time remainactive in the presence of high partial pressures of hydrogen sulfide andammonia.

Various catalyst systems have been used for upgrading lubricating oilsincluding hydrotreating catalysts of the type described in U.S. Pat.Nos. 3,078,221 and 3,078,238 to Beuther et al, which involve theprovision of a Group VI metal and Group VIII metal, such as a fluorinecontaining sulfided nickel and tungsten on a silica-aluminia carrier.Such catalysts have found wide commercial acceptance. More recently, animproved hydrotreating catalyst having a magnesia-alumina-aluminumphosphate support is described in U.S. Pat. No. 4,382,877 to Kehl. TheKehl catalyst possesses improved hydrodenitrification activity which isimportant for increasing catalyst life in the second stage of atwo-stage hydrotreating process, since the second stage catalyst isnormally more nitrogen-sensitive.

SUMMARY OF THE INVENTION

A catalyst composition has now been found, which composition comprisesan alumina-aluminum phosphate-silica support carrying a hydrogenationmetal component, such as a halogenated Group VI metal - Group VIIImetal, which possesses outstanding hydrodenitrification activity whilealso providing excellent conversion activity for hydroprocessing, suchas lubricating oil production. Surprisingly, it was found that thefluorided nickel-tungsten or alumina-aluminum phosphate-silica catalystof the present invention possesses hydrodenitrification activity farsuperior to that of a commercial fluorided nickel-tungsten catalyst. Aswill be hereinafter demonstrated, the catalyst of the present inventionpossesses hydrodenitrification activity which is more than twice that ofa commercial fluorided nickel-tungsten catalyst while providing the highviscosity index levels required of a good hydrotreating catalyst whenused for hydrotreating a heavy lubricating oil. Moreover, the presentcatalyst possesses over fifty percent more hydrodenitrification activitythan the improved magnesia-alumina-aluminum phosphate-supportedcatalyst, which will further improve the performance and life of thesecond stage catalyst of a two-stage hydrotreating process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS.

As indicated previously, the catalyst composition of the presentinvention comprises an alumina-aluminum phosphate-silica support. Thesupport of the present invention contains alumina in an amount of fromabout 2 to about 95 mole percent, preferably from about 50 to about 90mole percent, with from about 60 to about 80 mole percent beingespecially preferred. The aluminum phosphate is present in an amount offrom about 2 to about 95 mole percent, preferably from about 5 to about40 mole percent, and especially from about 10 to about 30 mole percent.The silica is present in an amount of from 0.1 to about 90 mole percent,preferably from about 1 to about 45 mole percent and especially fromabout 6 to about 20 mole percent. The alumina-aluminum phosphate-silicacan be prepared according to techniques and methods normally used in theart. One such method is set forth, for example, in U.S. Pat. No.3,904,550 to Pine, the disclosure of which is incorporated herein byreference. Another method is set forth in U.S. Pat. No. 4,080,311 issuedto Kehl, which discloses thermally-stable composite precipitatescontaining alumina and aluminum phosphate, as well as U.S. Pat. No.4,228,036 to Swift et al, which discloses a matrix of a zeolitecomposited with an alumina-aluminum phosphate-silica. The disclosures ofsuch patents are incorporated herein by reference.

The alumina-aluminum phosphate-silica of the present invention has thegeneral formula:

    Al.sub.2 O.sub.3 --AlPO.sub.4 --SiO.sub.2

and has an average pore radius of from about 10 Å to about 300 Å,preferably from about 20 Å to about 100 Å with from 20 Å to about 70 Åbeing especially preferred; a surface area ranging from about 50 squaremeters per gram to about 400 square meters per gram, preferably fromabout 150 square meters per gram to about 350 square meters per gramwith from about 250 to about 325 square meters per gram being especiallypreferred; and a pore volume of from about 0.1 cubic centimeters pergram to about 1.5 cubic centimeters per gram; preferably from about 0.3cubic centimeters per gram to about 1.2 cubic centimeters per gram withfrom about 0.35 to about 0.95 cubic centimeters per gram beingespecially preferred. The pore properties are measured by a standardnitrogen adsorption procedure based on the Brunauer, Emmett & Tellermethod, as modified by E. P. Barrett, L. G. Joyner and P. P. Halenda,"J.A.C.S.," 73, p.373 (1951).

The catalyst support of the present invention is provided with asuitable hydrogenation metal component for use as a hydroprocessingcatalyst. The preferred hydrogenation component comprises a halogencomponent in combination with Group VI and Group VIII metals. Althoughchlorine, bromine or iodine can be employed, fluorine is the mostpreferred halogen to be employed, and can be added, for example, in theform of hydrofluoric acid or ammonium fluoride. Suitable Group VI metalsinclude chromium, molybdenum and tungsten, while suitable Group VIIImetals include iron, cobalt and nickel. Such catalysts are described indetail in U.S. Pat. Nos. 3,078,221 and 3,078,238, the disclosures ofwhich are incorporated by reference. The total amount of the metalcomponent carried on the support of the present invention, as elementalmetal, will be in the range of from about 5 to about 50 weight percent,preferably from about 8 to about 30 weight percent. The preferredhydrogenation component is fluorine-nickel tungsten. The catalyst shouldcontain from about 0.3 to 4 weight percent, preferably 0.8 to about 2.5weight percent fluorine, based on the total catalyst weight.

The catalyst can be prepared in any desired manner. Preferably, thealumina-aluminum phosphate-silica support is provided in the form of anextrudate having an average diameter of from about 1/64 to about 1/4inch, preferably from about 1/32 to about 1/8 inch. The cross-sectionalconfiguration of the extrudate may be of any suitable form includingcircular, multiple lobes, e.g., trilobate, tetralobate, or can bestar-shaped, etc. The catalyst support is then impregnated with anaqueous solution of a compound of one or more of the above-describedmetals, preferably a salt thereof, such as the nitrate, sulfate,acetate, formate, ammonium salt or the hydroxide metal salt thereof.Alternatively, one or more of the metal salts can be added to thesupport prior to extrusion. Following impregnation of the extrudateswith an aqueous solution as required, the impregnated extrudate is driedat a temperature of from about 110° to about 130° C. to drive allvolatiles, such as water therefrom, and then calcined in air at atemperature of from about 350° to about 700° C. for about 1 to about 12hours.

The catalyst of the present invention can be used for hydroprocessing,e.g., hydrotreating, hydrocracking, hydrodenitrification, or the like.According to one preferred embodiment of the present invention, thepresent catalyst in presulfided form is used in a hydrotreating processto reduce the nitrogen and sulfur content and can also alter the chargestock, including saturation of aromatics, cracking of naphthenes andisomerization of paraffins to produce a lubricating oil. Suitablehydrotreating feedstocks include, for example, a refinery feed, such aslubricating oils, furnace oils, gas oils, or residuals, which can bepassed over the catalyst of the present invention at a liquid hourlyspace velocity (volume of liquid feed per volume of catalyst per hour,at ambient conditions of temperature and pressure) of about 0.25 toabout 4.0, preferably from about 0.35 to about 2.0, while maintainingthe reaction zone at a temperature of from 300° to about 500° C.,preferably from about 360° to about 440° C., while under a totalpressure of about 800 to about 4,000 pounds per square inch gauge (about5.6 to about 28.0 MPa), preferably from about 1500 to about 3500 poundsper square inch gauge (about 10.5 to about 24.5 MPa) and a hydrogenpartial pressure of from about 400 to about 4,000 pounds per square inchgauge (about 2.8 to about 28.0 MPa), preferably from about 750 to about3500 pounds per square inch gauge (about 5.2 to about 24.5 MPa).

According to another preferred embodiment of the present invention, thecatalyst of the present invention can be used in sulfided form in ahydrocracking process, which can, for example, comprise two stages toproduce diesel fuel, furnace oil, jet fuel, naphtha or the like. In thefirst stage, the catalyst of the present invention is used tohydrodenitrify the feedstock, while in the second stage, the catalyst isused to hydrocrack the denitrified feed. Suitable feedstocks for use inthe hydrocracking embodiment of the present invention include light orheavy gas oils, light fractions of crude oil, heavy fractions of crudeoil, or the like. Suitable hydrocracking conditions include those givenpreviously for hydrotreating.

Preparation and use of the catalysts of the present invention will beillustrated in the following examples.

EXAMPLES 1-6

An alumina-aluminum phosphate-silica support was prepared as follows.

A first solution was prepared by dissolving 7,500 grams of aluminumnitrate nonahydrate in 30 liters of distilled water. Next, 285 grams of85 weight percent phosphoric acid was added to the solution, and 3,636grams of silicic acid (1.65 percent silicon dioxide) were thereafteradded to the solution.

A stock solution of ammonium hydroxide was prepared by combining equalamounts of ammonium hydroxide and distilled water. The two solutionswere added to a mixing vessel equipped with an air-driven stirrer and apH probe from two separate burets while maintaining a constant pH of8.0. The mixing vessel was agitated for 10 minutes and the resultingproduct filtered. The filter cake was washed with 51 liters of watr, andthe washed filter cake was dried at 120° C. for more than 12 hours. Thedried granules from the filter cake were passed through an 80 meshscreen. The resulting granules contained 71.8 weight percent solids, and1,612 grams of the granules were blended with 11.57 grams ofmethylcellulose, an extrusion aid. Next 23.15 grams of concentratednitric acid and 200 cubic centimeters of distilled water were separatelyblended, and thereafter the granules, the methylcellulose and the nitricacid mixture and additional water to achieve a 40 weight percent solidmixture were thoroughly mixed for 1.5 hours.

The resulting mixture was extruded through a 1/16 inch diameter die andthe resulting extrudate was dried at 120° C. for over 12 hours.Thereafter, the extrudate was calcined for 10 hours at 538° C.

Additional samples of the alumina-aluminum phosphate-silica support wereprepared by varying the proportions of phosphoric and silicic acid. Thecatalyst support properties are set forth below in Table I for eachcatalyst support sample prepared, as well as for an alumina-aluminumphosphate-magnesia support for comparative purposes. The pore propertiesof the samples were measured by a standard nitrogen adsorption procedurebased on the Brunauer, Emmett & Teller method, as modified by E. P.Barrett, L. G. Joyner and P. P. Halenda, "J.A.C.S.," 73, p.373 (1951),the results of which are shown below in Table I:

                  TABLE I                                                         ______________________________________                                                     Example No.                                                                   1    2      3      4    5    6                                   ______________________________________                                        Components of Support,                                                        Mole Percent                                                                  Alumina        71     71     79   61   78   48                                Aluminum phosphate                                                                           20     20     11   17   22   37                                Silica         9      9      10   22   0    0                                 Magnesia       0      0      0    0    0    15                                Pore Data                                                                     Average Pore Radius, Å                                                                   43     43     24   66   61   124                               Pore volume, cc/g                                                                            0.64   0.64   0.37 0.92 0.66 1.04                              Surface area, m.sup.2 /g                                                                     300    300    311  280  215  168                               ______________________________________                                    

EXAMPLES 7-13

An impregnation solution was prepared by blending 60.68 grams of nickelnitrate, 52.85 grams of ammonium metatungstate, and 8.75 grams ofhydrofluoric acid in sufficient distilled water to form 135 cubiccentimeters of total solution. A 135.47 gram sample of the extrudedsupport of Example 1 was impregnated with the impregnation solution anddried at 120° C. for over 12 hours. The dried support was then calcinedat 538° C. for 10 hours. The resulting calcined catalyst is designatedCatalyst A. The impregnation procedure was repeated for each sample ofthe extruded support of Examples 3 and 4, respectively, and theresulting catalysts are designated Catalysts C and D, respectively. Theimpregnation procedure for the support of Example 2 (Catalyst B)differed slightly from the remaining catalysts, since the tungstencomponent was incorporated into the support prior to extrusion with theremaining components added by impregnation.

For comparative purposes, the impregnation procedure for Catalyst A wasrepeated using the support of Example 5 containing 78 mole percentalumina and 22 mole percent aluminum phosphate, but containing no silica(Catalyst E), and the support of Example 6, and alumina-aluminumphosphate-magnesia support (Catalyst F). Finally, a commercial catalystsample was prepared containing nickel, tungsten and fluorine on a silicaalumina support containing 75 weight percent silica and 25 weightpercent alumina (Catalyst G). Each of the catalyst samples to be testedcontained 6 weight percent nickel, 19 weight percent tungsten and 2weight percent fluorine.

Samples of the foregoing catalysts were evaluated in a microreactor testunit. Pretreatment involved contacting the catalyst with 2.1 standardcubic feet per hour of a gas stream containing 92 percent hydrogen and 8percent hydrogen sulfide at 400° F. (204° C.) and 35 psig (0.24 MPa)pressure for 4 hours. In addition, the catalyst was started up using2500 ppm sulfur as dimethyl sulfide in the feedstock and this sulfuraddition was maintained overnight at a reactor temperature of 600° F.(316° C.). Thereafter, a Kuwait heavy lubricating oil distillate waspassed over the catalyst at a temperature of 725° F. (385° C.), apressure of 2430 psig (17 MPa), a liquid hourly space velocity of 1.0together with a hydrogen stream. The gas circulation rate was 7500standard cubic feet of hydrogen per barrel. The data and test conditionsare summarized in Table II, below:

                                      TABLE II                                    __________________________________________________________________________                      Example No.                                                                   7   8   9   10  11  12  13                                                    Catalyst                                                    Properties  Feedstock                                                                           A   B   C   D   E   F   G                                   __________________________________________________________________________    Gravity, °API                                                                      18.3  30.5                                                                              28.2                                                                              29.2                                                                              27.5                                                                              27.2                                                                              26.5                                                                              26.1                                Sulfur, wt. %                                                                             3.6   0.013                                                                             0.036                                                                             0.012                                                                             0.053                                                                             0.036                                                                             0.10                                                                              0.43                                Nitrogen, wppm                                                                            1300  1.3 24  8.5 31  34  124 268                                 Liquid product                                                                            0     17.2                                                                              17.2                                                                              17.9                                                                              12.3                                                                              10.9                                                                              11.1                                                                              9.3                                 boiling below                                                                 650° F. (343° C.),                                              wt. %                                                                         VI of total dewaxed                                                                             121 110 119 131 109 98  105                                 oil @ 750° F. (399° C.)                                         __________________________________________________________________________

The test results set forth in Table II demonstrate that thealumina-aluminum phosphate-silica supported catalysts (Catalysts A-D)achieve significantly improved results over those of commercial catalyst(Catalyst G). For hydrodenitrification, Catalysts A-D were more than astwice as active as Catalyst G. Thus, Catalyst A achieved a reduction innitrogen from the 1300 ppm present in the feed to 1.3 ppm and Catalyst Dto 31 ppm, while the commercial Catalyst G achieved a reduction innitrogen to 260 ppm. Moreover, Catalysts A-D of the present inventionwere over 50 percent more effective as hydrodenitrification catalysts ascompared with the alumina-aluminum phosphate-magnesia catalyst (CatalystF) which reduced the nitrogen level to 124 ppm. Likewise, Catalysts A-Dwere more effective than Catalyst E which has just alumina-aluminumphosphate as the support. Moreover, incorporation of silica as inCatalyst C improved activity, as indicated by a higher viscosity indexof the product (119) over silica-free Catalyst E (109) which containedthe same amount of alumina, but in which one half of the aluminaphosphate has been replaced with silica.

The preparation method has some effect upon the activity of the finishedcatalyst. Catalysts A and B are identical in composition but differ inactivity as indicated by VI, nitrogen content and API gravity. CatalystA was prepared by impregnation of all active metals, which is thepreferred preparation method. The tungsten component of Catalyst B wasincorporated into the support before it was extruded, with the remainingcatalytic components being added by impregnation.

What is claimed is:
 1. A catalyst composition consisting essentially ofa coprecipitated alumina-aluminum phosphate-silica support formed bycoprecipitation of said alumina, aluminum phosphate and silica, saidsupport bearing a halogen, a Group VI metal and a Group VIII metalwherein said support consists essentially of alumina in the range offrom 50 to about 95 mole percent, aluminum phosphate in the range offrom about 2 to about 40 mole percent and silica in the range of fromabout 0.1 to about 45 mole percent, said halogen having been supplied tosaid support by impregnation.
 2. The catalyst composition of claim 1wherein said support has an average pore radius of from about 10 toabout 300 Å, a surface area of from about 50 to about 400 square metersper gram and a pore volume of from about 0.1 to about 1.5 cubiccentimeters per gram.
 3. The catalyst composition of claim 2 whereinsaid support has an average pore radius of from about 20 to about 100 Å,a surface area ranging from about 150 to about 350 square meters pergram and a pore volume of from about 0.3 to 1.2 cubic centimeters pergram.
 4. The catalyst composition of claim 3 wherein said support has anaverage pore radius of from about 20 to about 70 Å, a surface arearanging from about 250 to about 325 square meters per gram and a porevolume of from about 0.35 to about 0.95 cubic centimeters per gram. 5.The catalyst composition of claim 1 wherein said support consistsessentially of alumina in the amount of from about 60 to about 90 molepercent, and aluminum phosphate in the amount of from about 5 to about30 mole percent.
 6. The catalyst composition of claim 6 wherein saidsupport consists essentially of alumina in the amount of from about 60to about 80 mole percent, and aluminum phosphate in the amount of fromabout 10 to about 30 mole percent.
 7. The catalyst composition of claim1 wherein said halogen is fluorine, said Group VI metal is tungsten andsaid Group VIII metal is nickel.
 8. The catalyst composition of claim 7wherein said catalyst contains from 0.3 to 4 weight percent fluorine andsaid nickel and tungsten, in combination, are present in the range offrom about 5 to about 50 weight percent.
 9. The catalyst composition ofclaim 8 whereas said catalyst contains from 0.8 to 2.5 weight percentfluorine and said nickel and tungsten in combination are present in therange of from about 8 to about 30 weight percent.
 10. The catalystcomposition of claim 5 wherein said support consists essentially ofsilica in the amount of from about 1 to about 20 mole percent.
 11. Thecatalyst composition of claim 5 where said support consists essentiallyof silica in an amount of from about 6 to 22 mole percent.
 12. Thecatalyst composition of claim 1 wherein the halogen is fluorine.